1. Field of the Invention
The present arrangement relates to communication cables. More particularly, the present arrangement relates to jacket material for communication cables.
2. Description of the Related Art
In the United States, plastics used in the construction of plenum rated cables are regulated under the National Fire Protection Association standard NFPA 90A: Standard for the Installation of Air Conditioning and Ventilating Systems. Plenum cable is jacketed with a fire retardant plastic jacket of either a low-smoke polyvinyl chloride (PVC) or a fluorinated ethylene polymer (FEP). All materials intended for use on wire and cables to be placed in plenum spaces are designed to meet rigorous fire safety test standards in accordance with NFPA 262 and outlined in NFPA 90A.
Polyvinylidene Fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer. PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low smoke generation during a fire event. Compared to other fluoropolymers, it has an smoother melt process because of its relatively low melting point of around 155˜192° C. However, PVDF has a significant cost associated with it, making it less than ideal to use in its pure form.
To mitigate costs, prior cables have used a PVDF/PVC alloy composition for the jacket for both optical fiber and shielded data cable products. The PVDF is blended with PVC (lower cost) in order to reduce the cost of the finished compound while maintaining both the good flame properties and the mechanical properties of the PVDF. However, these PVDF/PVC alloys have problems with low temperature performance in the range of sub 0° C. temperatures due to the incompatibility of the two polymers. For example, the physical properties of the PVDF/PVC combination polymer jacket are extremely sensitive to manufacturing process variations, i.e. the two polymers do not weave/blend together, and thus the resulting cable jacket fractures easily in low temperatures. The prior art related to compatibilizers has not effectively addressed compatibilizers intended for plenum cables that have good low temperature performance.
Thus, although prior art plenum rated PVDF+PVC blends were available approximately 10 years ago, they were notorious for cracking at low temperatures. The present invention as claimed combines excellent flame and smoke performance with excellent low temperature properties.